On December 21, 1998, the Food and Drug Administration (FDA) licensed LYMErixTM
(SmithKline Beecham Biologicals, Reixensart, Belgium), * a new vaccine against Lyme
disease (LD). This report summarizes information about this vaccine and provides
epidemiologic information about LD relevant to vaccine use.

Each dose of LYMErixTM contains 30 ug of lipidated recombinant outer surface protein A
(OspA) of Borrelia burgdorferi sensu stricto, the causative agent of LD in North America,
adsorbed onto aluminum adjuvant (1). It is indicated for use in persons aged 15-70 years
(1). Three doses of the vaccine are administered by intramuscular injection. The initial
dose is followed by a second dose 1 month later and a third dose 12 months after the
first. Vaccine administration should be timed so the second dose and the third dose are
given several weeks before the beginning of the B. burgdorferi transmission season (1),
which usually begins in April. In a randomized, double-blind, multicenter trial involving
10,936 participants living in areas of the northeastern and upper north central United
States where LD is endemic, the vaccine efficacy in preventing LD was 50% (95% confidence
interval {CI}=14%-71%) after the first two doses and 78% (95% CI=59%-88%) after three
doses (1). Efficacy against asymptomatic seroconversion was 83% (95% CI=25%-96%) after two
doses and 100% (95% CI=30%-100%) after three doses (1). The duration of immunity following
the three-dose vaccination series is unknown, and the need for booster doses has not been
determined.

Local reactions at the site of injection were reported by significantly more vaccine
recipients than placebo recipients (1). Unsolicited reports of myalgia, influenza-like
illness, fever, and chills within 30 days after a dose were significantly more common
among vaccine recipients than placebo recipients, but none of these were reported by
greater than 5% of either group (1). Reports of arthritis were not significantly different
between vaccine and placebo recipients, but vaccine recipients reported significantly more
transient arthralgia and myalgia following each dose of vaccine (1).

LD is the most commonly reported vectorborne disease in the United States. Since the
implementation of a standardized surveillance case definition in 1991, greater than 90% of
cases have been reported from the northeast and north central states (Figure_1) (2). Persons of all ages are susceptible to infection,
but the highest reported rates of LD occur in children aged less than 15 years and adults
aged 30-59 years. Transmission peaks from April through July, when the nymphal stages of
the tick vectors of LD, Ixodes scapularis and I. pacificus, are actively seeking hosts.
These ticks are found primarily in leaf litter and low-lying vegetation in wooded, brushy,
or overgrown grassy areas and can transmit other diseases such as babesiosis and
ehrlichiosis (3,4).

An estimated 85% of persons with symptomatic LD have the characteristic rash, erythema
migrans (5). Untreated infection can cause arthritis or neurologic symptoms, such as
radiculoneuropathy or encephalopathy. At any stage, the disease can usually be
successfully treated with standard antibiotic regimens.

Strategies to prevent LD include avoiding tick habitats, wearing protective clothing,
using repellents to avoid tick attachment, promptly removing attached ticks, and employing
community measures to reduce tick abundance (6). Because the vaccine is less than 100%
efficacious and does not provide protection against other tickborne illnesses, vaccination
should not be considered a substitute for other preventive measures.

LD vaccine should be targeted to persons at risk for exposure to infected vector ticks.
This risk can be assessed by considering the focal geography of LD and the extent to which
a person's activities place him or her in contact with ticks (2). Vaccination of persons
with frequent or prolonged exposure to ticks in areas endemic for LD is likely to be an
important preventive strategy (7). For persons with only brief or intermittent exposure to
tick habitat in areas where LD is endemic, the public health benefits of vaccination,
compared with early diagnosis and treatment of LD, are not clear (7) . Recommendations for
use of LD vaccine are being developed by the Advisory Committee for Immunization
Practices.

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